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Description
INSERT SYSTEMSP
CUTTING WIDTH4 mm
INSERT POCKETS2
HEIGHT H26 mm
SPB 426 parting blade – technical data
Blade dimensions and compatible insert system
| Technical data | |
|---|---|
| Designation | SPB 426 |
| Type | double-ended blade |
| Insert system | SP (e.g., SP400) |
| Insert width | 4.0 mm |
| Height H | 26 mm |
| Height below the pocket H1 | 21 mm |
| Body thickness A | 3.2 mm |
| Length L | 110 mm |
| Insert pockets | 2 (at both ends) |
| Manufacturer | Varel |
Blade for parting and grooving – operating principle
Two pockets, spring clamping, body narrower than the insert
Parting blade SPB 426 is a double-ended blade for lathe use: it parts off bars and cuts external grooves. The SP carbide insert, 4 mm wide, sits in a spring-clamping pocket — held solely by the clamping force of the body, without a screw or wedge.
The body is 3.2 mm thick, which is less than the insert width. This prevents the sides of the blade from rubbing against the groove walls, even when cutting to full depth. Two pockets at opposite ends double tool life — when the first pocket wears out, turn the blade around and use the other end.
The blade has no engraved scale, so set the overhang with a caliper: measure the distance from the face of the block to the insert edge and compare it with the radius of the bar being parted off.
Keep the overhang as short as possible — only slightly greater than the radius of the bar being parted off. A shorter overhang means less blade deflection, less vibration, and a more even end face. During deep cuts, retract the insert every few millimeters to clear chips from the groove, and direct coolant straight into the cutting gap.
2 insert pockets
Worn pocket? Turn the blade 180° — the other end has its own insert pocket.
Spring clamping
The insert is held by the spring-clamping force of the body — without a screw or wedge. The pocket is opened with a blade wrench.
Body narrower than the insert
The insert is wider than the body, so the sides of the blade do not rub against the groove walls during deep cuts.
Blade dimensions – dimensional drawing
Side view and pocket cross-section
LENGTH L
110 mm
HEIGHT H
26 mm
THICKNESS A
3.2 mm
Tooling system – SP inserts and SMBB blocks
Step-by-step blade installation and compatible components
Installation in 3 steps
1Insert
seat SP400 using a blade wrench
2Block
secure the blade in the block SMBB
3Overhang
measure with a caliper, edge on centerline ±0.1 mm
✓Ready
parting and grooving with an insert 4 mm
Pocket system: SP (spring clamping)
COMPATIBLE WITH:
| ✓ | SP parting inserts — width 4.0 mm (e.g., SP400) |
| ✓ | SMBB series tool blocks — 5 sizes (listed below) |
| ✓ | Wrench for opening the blade pocket |
The blade pocket accepts SP inserts with a width of 4.0 mm, e.g., SP400. Inserts from other grooving families (DGN, GTN, 151.2) use different pockets and are not interchangeable — check the system designation before purchasing. A width of 4 mm provides a more rigid edge than 3 mm, allowing a higher feed and deeper cuts; material loss per cut increases to 4 mm.
SMBB series – five block sizes
| Block | Shank [mm] | Length [mm] | Compatible Varel blades (SP) | For this blade |
|---|---|---|---|---|
| SMBB 2026 | 20 | 87 | SPB 226 – 526 (height 26 mm) | FITS |
| SMBB 2032 | 20 | 100 | SPB 232 – 532 (height 32 mm) | |
| SMBB 2526 | 25 | 86 | SPB 226 – 526 (height 26 mm) | FITS |
| SMBB 2532 | 25 | 110 | SPB 232 – 532 (height 32 mm) | |
| SMBB 3232 | 32 | 110 | SPB 232 – 532 (height 32 mm) |
The first two digits in the block designation indicate the tool post shank height; the last two indicate the height of the blade held. The SPB 426 blade fits SMBB 2026 and SMBB 2526 blocks; blocks 2032, 2532, and 3232 accept blades with a height of 32 mm. Each block secures the blade with a screw-tightened clamp and allows continuous overhang adjustment along the scale.
Parting cutting data – speeds and feeds
Guideline values for inserts with a width of 4 mm
The values below are guidelines for coated SP inserts with a width of 4 mm, when machining with coolant. The applicable ranges are given in the grade data sheet for the specific insert.
| Workpiece material | Vc [m/min] | fn [mm/rev] |
|---|---|---|
| PCarbon steel | 120–200 | 0.13–0.35 |
| PAlloy steel | 100–170 | 0.13–0.35 |
| MStainless steel | 100–170 | 0.13–0.35 |
| KCast iron | 130–210 | 0.13–0.35 |
Spindle speed selection: n = (1000 × Vc) / (π × D). For a Ø30 mm carbon steel bar at Vc = 160 m/min: n = (1000 × 160) / (3.14 × 30) ≈ 1700 rpm — start at this speed and adjust based on chip shape.
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Operating limitations
The cutting depth is limited by the blade overhang from the block — extend it only as far as the bar radius requires, because every additional millimeter of overhang increases deflection and vibration. The cutting edge must be on the lathe centerline within ±0.1 mm: too high leaves a pip, while too low risks insert breakage. Over the final 2 mm before the centerline, reduce the feed to approximately 75%.
The SPB 426 parting blade combines a rigid body with a height of 26 mm and quick insert replacement in a spring-clamping pocket. Two insert pockets and compatibility with SP inserts with a width of 4 mm make it a basic tool for parting and grooving on a lathe.
Product accessories
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Shipping
All orders are delivered by courier company GLS. For orders exceeding 369 PLN gross shipping is FREE
| Courier GLS | Przelew24 / Prepayment | 14,76 zł gross | Delivery time 1 working day |
| Courier GLS | Cash on delivery | 17,26 zł gross | Lead time 1 working day |
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